My experience with D3D11on12 and Direct2D hasn't been that good. Infrequently I get
D3D12 ERROR: ID3D12Device::RemoveDevice: Device removal has been triggered for the following reason (DXGI_ERROR_ACCESS_DENIED: The application attempted to use a resource it does not access to. This could be, for example, rendering to a texture while only having read access.). [ EXECUTION ERROR #232: DEVICE_REMOVAL_PROCESS_AT_FAULT]
when I render to the swap chain backbuffer. There are lag spikes as well. And on top of all this, I think amortizing the "UI" will be needed when I try to push the frame rate.
Synchronization between the UI and the actual scene doesn't really matter, so I can happily just use whatever UI Direct2D has most recently finished rendering.
So I would like to use Direct2D to render the UI on a transparent D3D11on12 bitmap (i.e. one created by using CreateBitmapFromDxgiSurface with the ID3D11Resource from ID3D11On12Device::CreateWrappedResource). And then render this overlay this to the swapchain backbuffer.
The problem is I don't really know anything about the 3D pipeline, as I do everything with compute shaders/DirectML + CopyTextureRegion or Direct2D. I suppose this is a pretty simple question about how to do alpha blending.
I suppose to do alpha blending you have to use the 3D pipeline. Luckily enough directXTK12 seems to do a tutorial that is reasonable trivial on this topic https://github.com/Microsoft/DirectXTK12/wiki/Sprites-and-textures